In June 2015, Taylor wrote an open letter to Apple and its CEO, Tim Cook. In the note, she took the company to task for its decision not to pay artists during an initial three-month free trial of Apple Music, the then new streaming service Apple was launching the following Tuesday.

Taylor wrote:

"I’m sure you are aware that Apple Music will be offering a free 3 month trial to anyone who signs up for the service. I’m not sure you know that Apple Music will not be paying writers, producers, or artists for those three months. I find it to be shocking, disappointing, and completely unlike this historically progressive and generous company." -- Taylor Swift

The letter was polite and to the point. Taylor felt it unfair for Apple to use artists, especially up-and-coming ones, to grow its new service without compensating them for it. The counterargument, meanwhile, held that the free trial could bring lots of free publicity to those same lesser-heard artists. The flaw there, however, was that Apple was asking those artists to make a leap of faith in the hopes of more followers and money in the future -- but many small artists live essentially paycheck to paycheck, and they can’t stomach a quarter of reduced payouts.

So in one of the most amazing changes of direction in the history of Apple as well as the entire music industry, Taylor’s letter -- and the public show of support it drummed up -- got Apple to change its mind. Just hours after the note went up, Apple announced it would indeed be paying artists for their music during the free period, if at a reduced rate (other streaming services have similar practices).

You might think Taylor’s Apple-shaming would be a public relations disaster for the company -- and at first, this is how it was portrayed in the media. But in an ironic twist, Taylor’s move was wonderful for Apple and its new music service.

Before her letter, only music and tech industry followers seemed truly aware of Apple Music’s imminent launch. It seemed like Apple would need to do lots of promotion to get significant numbers of users on board -- die-hard Apple fans might have been good for as many as 15 million users off the bat, but not more than that. Because of Taylor’s letter, millions more potential users were now aware of the service.

But her letter did something else for Apple, too. At Fortune, fellow Apple-watcher Philip Elmer-Dewitt wrote that “the Taylor Swift effect continues to ripple across the music industry.” Elmer-Dewitt continued:

"According to Billboard, two independent music umbrella groups -- the digital rights organization Merlin and Martin Mills’ Beggars Group -- have dropped their resistance to the new Apple Music streaming service set to begin next week. Merlin and Beggars are long-tail powerhouses. Merlin represents some 20,000 independent music labels and distributors. Beggars, which dates back to the young Rolling Stones, launched the careers of Adele, Jack White, M.I.A." -- Philip Elmer-Dewitt

More artists who resisted putting their music on Apple Music are now changing their tune -- thanks, in part, to Taylor.

What she ultimately did was create a win-win scenario for herself, Apple, and all artists who now have a powerful outlet to showcase their musical talents.